Partially disulfonated hydroquinone (HQ)-based poly(arylene ether sulfone) random copolymers were synthesized and characterized for application as proton exchange membranes. The copolymer composition was varied in the degree of disulfonation. The copolymers were characterized by H-1 NMR, Differential Scanning Calorimetry (DSC), and other analytical techniques. The copolymer with a 25% degree of disulfonation showed the best balance between water uptake and proton conductivity. The copolymers showed substantially reduced methanol permeability compared with Nafion (R) and satisfactory direct methanol fuel cell performance. The methanol selectivity improved significantly in comparison to Nafion (R) 117. At a given ionic composition, the HQ-based system showed higher water uptake and proton conductivity than the biphenol-based (BPSH-xx) poly(arylene ether sulfone)s copolymers. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 384-391, 2009